The Effect of Rural Buildings on Landscape Fragmentation
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sustainability Article The Effect of Rural Buildings on Landscape Fragmentation in Natura 2000 Sites: A Case Study in Sardinia Antonio Ledda 1 , Vittorio Serra 2 and Andrea De Montis 1,2,* 1 Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy 2 Department of Civil and Environmental Engineering and Architecture, University of Cagliari, via Marengo 2, 09123 Cagliari, Italy * Correspondence: [email protected]; Tel.: +39-079-229242 Received: 30 July 2019; Accepted: 23 August 2019; Published: 28 August 2019 Abstract: Landscape fragmentation (LF) is the process where habitat patches tend to become smaller and more isolated over time. It is mainly due to human activities and affects habitats, biodiversity, ecosystem balance, and ecological networks. Transport and mobility infrastructures and urbanized areas—also in the form of suburban and rural sprawl—contribute to LF and can be localized close to (or included in) Natura 2000 sites (N2000 sites). N2000 sites are set according to the Habitats and Birds Directives and consist of special protection areas, sites of community importance, and special areas of conservation, where LF may threaten habitat quality and species survival and dispersal. Then, new rules and planning approaches are called for defining effective protection measures. The knowledge of the context appears to be a priority to achieve such aims. Therefore, this study focuses on LF in N2000 sites. We apply the rural buildings fragmentation index (RBFI) and the effective mesh density (Seff) in six landscape units in Sardinia (Italy). Then, we report on the least and the most fragmented N2000 sites and assess if there is correlation between RBFI and Seff. In this study, RBFI and Seff provide not trivial outcomes, as they are weakly and positively correlated. Keywords: Italy; Sardinia; rural buildings; protection and conservation areas; landscape fragmentation; habitat loss; rural buildings fragmentation index (RBFI); effective mesh density (Seff); comparative analysis 1. Introduction Human actions are acknowledged as major drivers affecting landscape quality. Deforestation, transport and mobility infrastructures (TMIs), and land conversion for agricultural, industrial, and urban uses influence habitat quality, ecosystems balance, and biodiversity [1,2]. Harmful effects include landscape fragmentation (LF)—i.e., the process where habitat patches tend to become smaller and more isolated [1]. LF characterizes urbanized contexts, where TMIs [1,3,4] and urban settlement [5] trigger habitat loss and contribute in reducing size and isolating habitat patches. LF affects flora and wild fauna [6] in both the long and short run and can lead to population extinction. Ecological networks are also affected by urbanized areas [7,8], in that buildings and TMIs are elements that contribute to soil consumption or, in other terms, to natural habitat (con-)diversion for human uses. Conservation of habitats has been acknowledged as a matter of primary importance by the scientific community for a long while [9–11]. In response to such a need, the Council of the European Communities enacted the ‘Habitat Directive’ (Directive 92/43/EEC; [12]), which focuses mainly on the protection of biodiversity and the preservation of natural habitats for wild flora and fauna in the European continent. A cornerstone of this act is the establishment of the Natura 2000 (hereafter noted as Sustainability 2019, 11, 4695; doi:10.3390/su11174695 www.mdpi.com/journal/sustainability Sustainability 2019, 11, 4695 2 of 18 N2000) network, which is projected to include special conservation areas and special protection areas, the latter one is defined according to the ‘Birds Directive’ (Directive 2009/147/EC; [13]). As a whole, sites of community importance (SCIs), special areas of conservation (SACs), and special protection areas (SPAs) constitute N2000 sites. According to the N2000 barometer statistics (release version End2018—15 March 2019), N2000 land areas extend for more than 784,000 km2, while N2000 marine areas for more than 551,000 km2 [14]. In Italy, N2000 land and marine areas extend, respectively, for more than 57,000 km2 and 6800 km2. In Italy, N2000 network includes more than 2600 sites. As for the island of Sardinia, 56 SACs have been set according to the Decree of the Italian Ministry of the Environment [15], and N2000 sites are receiving growing attention by scholars [16–18]. N2000 sites most of the times include rural areas. Rural and peri-urban contexts are characterized by rural buildings, which are settled according to three main forms: (i) Sprinkling [19,20], (ii) rural, and (iii) urban or suburban sprawl [21]. Romano et al. define ‘sprinkling’ as “[land] take with a partially spontaneous development, or subject to low controls, adding on to a historical structure. The built-up areas are not homogeneous in size and use, with a mixture of rural, residential, [ ::: ] functions [ ::: ]” [19] (p. 4). Sprinkling is quite common in Italy, but also in southern Europe [19]. Rural sprawl refers to housing expansion far from urban settlements [21]. According to the Encyclopaedia Britannica, urban or suburban sprawl means “the rapid expansion of the geographic extent of cities and towns, often characterized by low-density residential housing, single-use zoning, and increased reliance on the private automobile for transportation” [22]. Rural sprawl and sprinkling play a non-marginal role in increasing habitat loss and triggering LF processes [19,21,23]. Metrics specifically proposed to quantify LF caused by rural buildings are scarcely discussed in scientific literature. Then, this research focuses on the influence of the built-up rural dimension on LF in areas protected by N2000 network, given its relevance for habitats and species protection and conservation. The idea is that LF assessment is key to addressing suitable policies, with respect to ecosystem preservation and ideal functioning. Starting from [24] we aim at measuring the dynamics of LF in six landscape units (LUs) set by the Regional Landscape Plan (RLP) of Sardinia (Italy) [25] by applying two indices: The rural buildings fragmentation index (RBFI, see [26] and the effective mesh density (Seff)[1]. In addition, we apply the average nearest neighbor (ANN) approach [27,28] to investigate on the interplay between built-up spatial pattern and LF. In detail, we aim at answering two research questions (RQs). RQ1 concerns the measure of LF due to rural buildings in N2000 sites by using the RBFI, while RQ2 regards the correlation between RBFI and Seff. RQ1 allows us to figure out if and to what extent the RBFI is affordable in measuring LF. In this vein, we apply the RBFI in a rural context interested by N2000 sites. We would expect to find low levels of LF in these areas, since the N2000 network should promote habitat and species conservation. RQ2 focuses on the RBFI and its correlation with the Seff, which is a well-known metric. We aim at understanding if the RBFI confirms, integrates, or negates the findings we can obtain by applying the Seff. In the next section, we report on the scientific literature concerning LF and habitat loss due to rural buildings and LF in N2000 sites, illustrate metrics, data and software used, and describe the study areas. In the third and fourth sections, we show and—respectively—discuss the findings. Finally, in the fifth section we report on the concluding remarks. 2. Materials and Methods In this section, we reported on the main scientific studies concerning LF in N2000 sites and habitat loss caused by rural buildings, metrics and data and software used, and the characteristics of the study areas. 2.1. Literature Review Summary Human infrastructures and settlements are key factors in LF [5,6] and affect protected areas and biodiversity [2]. Some scholars stress that further research is needed to investigate deeply “fragmentation at landscape scales” [29] (p. 272). Sustainability 2019, 11, 4695 3 of 18 LF in N2000 sites has attracted the interest of international scholars. Hernando et al. [30] measured LF in Spain through a morphological spatial pattern analysis and report on the importance of the forest cover map resolution for assessing habitat conservation status. The authors stress that: (i) The resolution of input cover maps affects the findings of morphological spatial pattern analysis and (ii) the appraisal of habitat conservation depends on the spatial resolution of cover maps [30]. Piquer-Rodríguez et al. [31] consider land-use change as a factor affecting connectivity of protected areas and focus on the province of Almería, Andalusia, in southeastern Spain. The authors proposed and applied a method consisting of the integration of spatially land-use models with LF analyses “in order to assess the effects of future land use on the connectivity of current protected area networks” [31] (p. 327). The morphological spatial pattern analysis was used to measure LF. The authors stated that conservation planning should consider the future land use orientation, because it has relevant relations with connectivity and resilience. Tomaselli et al. [32] apply several LF metrics in three coastal wetlands included in N2000 sites instituted in Apulia (Italy). The authors used the well-known software FRAGSTATS [33] to process LF metrics and “investigate [the reliability of the metrics] in assessing fragmentation and spatial patterns of habitats” [32] (p. 693). Most of the times, N2000 sites are localized in rural areas, where TMIs and rural settlement contribute to LF and, thus, loss of natural and semi-natural habitats. In this study, we considered the rural sprawl as a factor that contributes in increasing habitat loss and LF. Suburban sprawl is characterized by higher housing density (housing units/km2) than the rural sprawl [34]. The latter one affects “much larger areas than suburban sprawl” [34] (p. 794) since it exerts on each house remarkable and harmful environmental effects that take place in less altered contexts [34]. According to Hansen et al. [35] (p. 1893), “many native species have reduced survival and reproduction near homes” in low-density rural home settlement (from 6 to 25 houses/km2).